Embodiments of the present invention relate generally to an apparatus and method corresponding to a transceiver chip that is part of an optical serial data communications system, and more particularly to automatic recovery within the transceiver chip.
High-speed digital communication networks over copper and optical fiber are used in many network communication and digital storage applications. Ethernet and Fibre Channel are two widely used communication protocols used today and continue to evolve to respond to the increasing need for higher bandwidth in digital communication systems.
The Open Systems Interconnection (OSI) model (ISO standard) was developed to establish standardization for linking heterogeneous computer and communication systems. The OSI model includes seven distinct functional layers including Layer 7: an application layer; Layer 6: a presentation layer; Layer 5: a session layer; Layer 4: a transport layer; Layer 3: a network layer; Layer 2: a data link layer; and Layer 1: a physical layer. Each OSI layer is responsible for establishing what is to be done at that layer of the network but not how to implement it.
Layers 1 to 4 handle network control and data transmission and reception. Layers 5 to 7 handle application issues. Specific functions of each layer may vary to a certain extent, depending on the exact requirements of a given protocol to be implemented for the layer. For example, the Ethernet protocol provides collision detection and carrier sensing in the data link layer.
The physical layer, Layer 1, is responsible for handling all electrical, optical, and mechanical requirements for interfacing to the communication media. The physical layer provides encoding and decoding, synchronization, clock data recovery, and transmission and reception of bit streams. Typically, high-speed electrical or optical transceivers are the hardware elements used to implement this layer.
The Synchronous Optical Network (SONET) is an interface standard for synchronous optical fiber transmission, applicable to the Physical Layer of the OSI Reference Model.
SONET comprises a set of signal rates for transmitting and receiving serial digital data signals over optical fiber. The base rate (OC-1) is 51.84 Mbps. Multiples of the base rate are also provided. For example:                OC-3 (155.52 Mbps)        OC-12 (622.08 Mbps)        OC-48 (2.488 Gbps)        
Transceiver chips may typically be characterized as comprising two sections that interface between a line-side of a communication link and a system-side of the communication link. An inbound section receives data from the line-side of the communication link and processes and passes the data to the system-side of the communication link. An outbound section receives data from the system-side of the communication link and processes and passes the data to the line-side of the communication link. The line-side of the outbound section of the transceiver chip typically transmits the data in a serial format to an electrical-to-optical converter which transmits the data over a fiber optic cable. The system-side of the outbound section of the transceiver chip typically receives parallel or serial digital data from a system framer or ASIC.
When data is being received into the outbound section of the transceiver chip from the system-side, the data is clocked into the transceiver chip on the system-side by a primary clock signal. Typically, if a problem occurs with the primary clock signal, the chip may hang, and the entire outbound section of the transceiver chip must be reset to an initial state by way of outside system level intervention. The system level reset process may take an undesirably long time and corrupted data may be transmitted out of the line-side of the outbound section of the transceiver chip.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.